Abstract:
Changes in climatic conditions are expected globally resulting in a higher rainfall intensity
and longer duration of rainfall. The increase in the rainwater infiltration into the soil contributes to
many geotechnical issues, such as excessive settlement, retaining wall failure and rainfall-induced
slope failures. These geotechnical problems could be mitigated by the improvement of the problematic
soil with the incorporation of the unsaturated soil mechanic principles. Dual-porosity soils or soils
with bimodal water retention curve (WRC) are able to retain more water during prolonged drying
and they would be able to drain out water faster during intense rainfall to maintain the slope stability.
The objective of this study is to investigate the characteristics of the unsaturated shear strength of
soil with bimodal WRC. In addition, the new mathematical equation is proposed to estimate the
unsaturated shear strength of soils with a bimodal WRC. The results of the study indicated that the
nonlinearity of the unsaturated shear strength is a function of the shape of bimodal WRC limited by
the first and second air-entry value (AEV) of dual-porosity soils. The proposed equation agreed well
with the experimental data of the unsaturated shear strength for dual-porosity soil.